Device longevity prediction for a device having variable energy consumption

ABSTRACT

A system and method for estimating the longevity of an implantable medical device (IMD). In one embodiment of a method for estimating a life of a power source of an implantable medical device, a first life estimate of the power source is determined based on a first open-loop value corresponding to an open-loop parameter for open-loop therapy delivery, a first closed loop value corresponding to a closed-loop parameter for closed-loop therapy delivery, and prior usage data corresponding to prior therapy delivery. The first life estimate of the power source is displayed. The first life estimate displayed includes a first open-loop portion associated with open-loop therapy delivery and a first closed-loop portion associated with closed-loop therapy delivery.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 14/276,652, filed May 13, 2014 which is adivisional application of U.S. patent application Ser. No. 13/086,667,filed Apr. 14, 2011 and issued as U.S. Pat. No. 8,671,884.

BACKGROUND

Medical treatments for disorders of the nervous system, such as seizuredisorders (e.g., epilepsy), have improved in recent decades. Oneavailable treatment involves the application of an electrical signal toreduce various symptoms or effects caused by such neural disorders. Forexample, electrical signals have been successfully applied at strategiclocations in the human body to provide various benefits, including areduction of seizure occurrence and the improvement of other medicalconditions. An example of such a treatment regimen involves theapplication of electrical stimulation to the vagus nerve of the humanbody to reduce or eliminate epileptic seizures, as described in U.S.Pat. No. 4,702,254, which is incorporated herein by reference.

Electrical stimulation of a target tissue of a patient's body may beprovided by implanting an electrical device (known as an implantablemedical device, or “IMD”) underneath the skin of a patient andelectrically stimulating the target tissue. In some cases, electricalstimulation of target tissue (including, but not limited to neuraltissue such as the vagus nerve) may be delivered in accordance with aprogrammed (or predetermined or “planned”) schedule. In such cases, theelectrical stimulation is referred to as “open-loop,” “passive,”“programmed,” or “non-feedback” stimulation. In other cases, electricalstimulation may be delivered in response to detecting some type ofevent. In one embodiment, the event may be patient-initiated, i.e., thepatient may manually initiate stimulation by performing an action thatis detected as an event (“manually-initiated” or “manually-requested”stimulation). In another embodiment, a change in one or more bodyparameters (for example, cardiac rhythm, muscle activity, or bodymovements) may be detected as an event that triggers electricalstimulation. Typically, the body parameter(s) is selected such that thechange in the parameter is indicative of a disease state such as anepileptic seizure. Stimulation initiated based on a detected change in abody parameter is referred to as “automatic” or“automatically-initiated” stimulation. Event based stimulation, whichincludes manually initiated and/or automatic stimulation, is known as“closed-loop,” “active” or “feedback” stimulation. In some devices, bothopen-loop and closed-loop stimulation may be simultaneously employed,with an open-loop program operating to provide a basic level of therapyand closed-loop stimulation provided in response to episodic events.

Whether delivered as closed-loop or open-loop, the stimulation istypically applied as a sequence of pulses (collectively referred to as a“burst”) extending for a defined duration (known as the “on-time” or“burst duration”). In open-loop stimulation, the pulse bursts areseparated by a programmed time period (the “off-time”), and inclosed-loop stimulation the bursts are delivered in response to thedetected event and may include a refractory period after the closed-loopburst to allow the nerve to recover. During the on-time of a pulseburst, electrical pulses of a defined electrical current (e.g., 0.5-3.5milliamps) and pulse width (e.g., 0.25-1.0 milliseconds) are deliveredat a defined frequency (e.g., 20-30 Hz) for the burst duration (e.g.,7-60 seconds). For open-loop stimulation, the on-time and off-timeparameters together define a duty cycle, which is the ratio of theon-time to the combination of the on-time and off-time, and whichdescribes the percentage of time that the electrical signal is appliedto the nerve.

Most IMDs are powered by onboard batteries; consequently, the amount ofpower available is finite. Just before the battery of an IMD isexhausted, the IMD must be surgically removed from a patient's body sothat a new device (or battery) may be installed. For this reason, theability to accurately predict a battery's remaining life is crucial toensuring that therapy to the patient is not interrupted, and to avoidendangering the patient's health. Overestimating an IMD's battery lifecan result in the undesirable interruption of therapy caused by notreplacing the IMD and/or battery prior to exhaustion of its electricalcharge. On the other hand, underestimating an IMD's battery life canresult in surgery that is not then necessary, and a waste of the usefullife of the IMD.

Predicting battery life generally is relatively uncomplicated when anIMD only applies electrical pulses in accordance with a planned schedule(“open-loop” stimulation). When closed-loop stimulation is used (eitheralone or in combination with open-loop stimulation), predicting batterylife becomes difficult, because closed-loop stimulation ispatient-specific and does not occur according to any predeterminedschedule.

Thus, methods and systems for accurately predicting battery life in IMDsthat apply closed-loop stimulation are desired.

SUMMARY

A system and method for estimating the longevity of an implantablemedical device (IMD). In one embodiment, a method for estimating a lifeof a power source of an implantable medical device includes determininga first life estimate of the power source based on a first open-loopvalue corresponding to an open-loop parameter for open-loop therapydelivery, a first closed loop value corresponding to a closed-loopparameter for closed-loop therapy delivery, and prior usage datacorresponding to prior therapy delivery. The first life estimate of thepower source is displayed. The first life estimate displayed includes afirst open-loop portion associated with open-loop therapy delivery and afirst closed-loop portion associated with closed-loop therapy delivery.

In another embodiment, a system for estimating a life of a power sourceof an IMD includes therapy logic, detection logic, and a control device.The therapy logic is configured to provide open-loop therapy andclosed-loop therapy to the patient. The detection logic is coupled tothe therapy logic. The detection logic includes an algorithm configuredto detect an event for triggering closed-loop therapy, and to recorddetected events. The control device is coupled to the therapy logic andthe detection logic. The control device is configured to provide a firstoperable life estimate of the power source of the IMD. The firstoperable life estimate identifies a first open-loop therapy portion ofthe first life estimate and a first closed-loop therapy portion of thefirst life estimate.

In yet another embodiment, a method includes determining a firstoperable life estimate of an IMD. The first operable life estimate isbased on a first operable life reduction attributable to a number ofdetected events operative to trigger closed-loop therapy and a secondoperable life reduction attributable to open-loop therapy. For the firstoperable life estimate, a first open-loop therapy portion associatedwith the second operable life reduction and a first closed-loop therapyportion associated with the first operable life reduction areidentified.

In a further embodiment, an apparatus for controlling an IMD having apower source includes a processor and a display device. The processor isoperative to generate an operable life estimate for the power sourcebased on a number of open-loop therapies delivered during a first timeperiod, a number of closed-loop therapy detection events during thefirst time period, a charge consumption associated with each open-looptherapy delivery; and a charge consumption associated with eachclosed-loop therapy delivery. The operable life estimate includes anopen-loop therapy portion corresponding to operable life of the IMD usedfor open-loop therapy delivery and a closed-loop therapy portioncorresponding to the operable life of the IMD used for closed-looptherapy delivery. The display device is coupled to the processor. Thedisplay device is operative to display the operable life estimategenerated by the processor including the open-loop therapy portion andthe closed-loop therapy portion.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of exemplary embodiments of the presentdisclosure, reference will now be made to the accompanying drawings inwhich:

FIG. 1 shows an illustrative stimulation system coupled to a humancranial nerve in accordance with various embodiments;

FIG. 2 shows a block diagram of the implantable medical device as shownin FIG. 1, in accordance with various embodiments;

FIG. 3 shows a block diagram of the control unit, as shown in FIG. 1, inaccordance with various embodiments;

FIGS. 4A-4D shows exemplary graphical displays provided by the controlunit, as shown in FIG. 1, in accordance with various embodiments; and

FIG. 5 shows a flow diagram of an illustrative method for predictinglongevity of the implantable medical device, as shown in FIG. 1, inaccordance with various embodiments.

NOTATION AND NOMENCLATURE

Certain terms are used throughout the following description and claimsto refer to particular system components. As one skilled in the art willappreciate, companies may refer to a component by different names. Thisdocument does not intend to distinguish between components that differin name but not function. In the following discussion and in the claims,the terms “including” and “comprising” are used in an open-endedfashion, and thus should be interpreted to mean “including, but notlimited to . . . . ” Also, the term “couple” or “couples” is intended tomean either an indirect or direct electrical connection. Thus, if afirst device couples to a second device, that connection may be througha direct electrical connection, or through an indirect electricalconnection via other devices and connections. Further, the term“software” includes any executable code capable of running on aprocessor, regardless of the media used to store the software. Thus,code stored in memory (e.g., non-volatile memory), and sometimesreferred to as “embedded firmware,” is included within the definition ofsoftware.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of thepresent disclosure. The embodiments disclosed should not be interpreted,or otherwise construed, as limiting the scope of the disclosure,including the claims. In addition, one skilled in the art willunderstand that the following description has broad application, and thediscussion of any embodiment is meant only to be exemplary of thatembodiment, and not intended to intimate that the scope of thedisclosure, including the claims, is limited to that embodiment.

While accurately predicting battery life in an implantable medicaldevice (IMD) that delivers both open-loop and closed-loop therapy may bedifficult, reliable longevity information is important for use in tuningIMD operation to achieve a target IMD operational life, and forscheduling IMD replacement. Embodiments of the present disclosureprovide device longevity estimates in a graphical form that highlightsthe effects of open-loop and closed-loop therapy on IMD operationallife. Embodiments are configured to gather closed-loop operationalinformation from an implanted IMD and model the effects of closed-looptherapy on IMD life. Embodiments also allow investigation of the effectsof closed-loop therapy with no corresponding reduction in operable IMDlife. Various embodiments are now described in detail with reference tothe figures.

FIG. 1 illustrates an implantable medical device 110 having a main body112 comprising an enclosure or can 121 with a connector 114 (alsoreferred to as the header) for connecting to leads 122. The IMD 110 isimplanted in a patient's chest in a pocket or cavity formed by theimplanting surgeon just below the skin, similar to the implantationprocedure for a pacemaker pulse generator. A stimulating nerve electrodeassembly 125, preferably comprising an electrode pair, conductivelycouples to the distal end of an insulated and electrically conductivelead assembly 122, which preferably comprises a pair of lead wires (onewire for each electrode of an electrode pair). Lead assembly 122 isattached at its proximal end to the connector 114 on can 121. Theelectrode assembly 125 is surgically coupled to a cranial nerve, such asa vagus nerve 127 in the patient's neck. The electrode assembly 125preferably comprises a bipolar stimulating electrode pair, such as theelectrode pair described in U.S. Pat. No. 4,573,481, which isincorporated herein by reference. Persons of skill in the art willappreciate that many electrode designs could be used in embodiments ofthe present disclosure. The two electrodes are preferably wrapped aroundthe vagus nerve, and the electrode assembly 125 preferably is secured tothe nerve 127 by a spiral anchoring tether such as that disclosed inU.S. Pat. No. 4,979,511, which is incorporated herein by reference. Leadassembly 122 may be secured, while retaining the ability to flex withmovement of the chest and neck, by a suture connection to nearby tissue.

The IMD 110 may be controlled or programmed with a control unit 150(e.g., a computer including any type of stationary, mobile, or handheldcomputing device) and a programming wand 155 to facilitate wirelesscommunication between the control unit 150 and the IMD 110. Theprogramming wand 155 permits noninvasive communication with the IMD 110after the latter is implanted. In systems where the control unit 150uses one or more channels in the Medical Implant Communications Service(MICS) bandwidths, the programming wand 155 may be omitted to permitmore convenient communication directly between the control unit 150 andthe IMD 110.

In at least some embodiments of the present disclosure, an estimate oflongevity of a power source powering the IMD 110 is first made with theIMD 110 programmed to deliver only open-loop therapy, and to record whenclosed-loop therapy would have been delivered had closed-loop therapybeen enabled. The recorded data may be provided to the control unit 150in real-time or may be stored in IMD 110 for subsequent transfer to thecontrol unit 150. The recorded data can then be used to estimate powersource longevity. The estimation may be used to adjust IMD 110parameters in consideration of estimated power source longevity and, ifdesired, closed-loop stimulation may thereafter be enabled. Furthermore,the estimation may be used to adjust IMD 110 parameters in considerationof estimated power source longevity in both the presence and absence ofclosed-loop therapy.

Alternatively, an initial longevity estimate is based on both anopen-loop therapy program and predicted closed-loop therapy (based onthe patient's personal medical condition history, event detectorperformance capabilities, and/or one or more of a variety of otherfactors). The initial longevity estimate may occur using the IMD 110 andthe control unit 150, or it may occur in a surrogate environment, suchas a computer based simulation. Subsequently, the rate of closed-looptherapy that is actually provided by the IMD 110 while the IMD 110 isimplanted and operating inside the patient's body (i.e., the rate ofclosed-loop therapy “in real life”) is recorded within the IMD 110 andlater provided to the control unit 150 and used to adjust the estimateof power source longevity. Alternatively, the log may be provided inreal-time to the control unit 150. In either case, the actualclosed-loop therapy data is used to refine the initial estimateregarding longevity of the IMD 110.

Initial estimates and refinements thereto preferably are performed bythe control unit 150 but also may be performed by the IMD 110. In somecases, portions of the initial estimates and/or refinements may beperformed by the IMD 110 with the remainder of the estimates and/orrefinements performed by the control unit 150. Both the initialestimates and refined predictions are displayed or otherwise provided toan end-user of the control unit 150 (e.g., the patient's physician). Theend-user, such as the physician or patient, may adjust IMD 110closed-loop algorithm parameters (e.g., event detection thresholds,stimulation current, etc.) in light of the estimated longevity and/orefficacy of the current therapy. The end-user also may enable or disableresponsive, closed-loop therapy by the IMD 110. Further, the end-usermay adjust the open-loop parameters (e.g., frequency, amplitude, pulsewidth) or disable open-loop therapy based on the performance andprediction information provided about all modes of therapy.

The IMD 110 illustrated in FIG. 1 provides electrical stimulation to acranial nerve, such as the vagus nerve. However, the embodiments of thepresent disclosure are not limited to implantable devices that deliverelectrical stimulation to a cranial nerve. Therapy may be delivered toany nerve, tissue, structure, or system of the body. Furthermore, theembodiments of the present disclosure are not limited to implantabledevices that deliver electrical stimulation as a therapy. Any other typeof therapy delivered by an implantable device may be used, such as adrug/chemical dosage delivery therapy, mechanical therapy (e.g.,vibrations), optical, sound, or any other type of electromagneticradiation therapy, or combination thereof.

FIG. 2 illustrates a block diagram of IMD 110 for performingneurostimulation in accordance with embodiments of the presentdisclosure. In one embodiment, the IMD 110 comprises a power source 210,a power-source controller 220, a stimulation controller 230, a powerregulation unit 240, a stimulation unit 250, a communication unit 260,and storage 280. The stimulation controller 230 and stimulation unit 250together form stimulation logic 255.

Storage 280 may be used for storing various program codes, startingdata, and the like. More specifically, the storage 280 stores theparameter values that govern the rate and level of stimulation providedby the stimulation logic 255. The stored parameter values also enabledelivery and/or logging of stimulation administered or events detectedbased on the different categories of stimulation (e.g., open-loop,automatically-initiated, manually-initiated). Information regarding thestimulation administered and/or stimulation trigger events detected isstored as stimulation data and counts 282 in the storage 280. Thestimulation data and counts 282 may comprise a count of open-loopstimulations administered, a count of automatic stimulation triggerevents detected, a count of automatic stimulation events administered, acount of received manually-initiated stimulation requests, and a countof manually-initiated stimulations delivered. The stored count valuesmay be provided to the control unit 150 to facilitate prediction of theoperational life of the IMD 110.

The power source 210 may comprise a battery, which may be rechargeableor non-rechargeable. Other power sources, such as capacitors, may alsobe used. The power source 210 provides power for the operation of theIMD 110, including electronic operations and stimulation bursts. Powersource 210, in one embodiment, may be a lithium-thionyl chloride cell ora lithium/carbon monofluoride (LiCFx) cell. The terminals of the powersource 210 preferably electrically couple to an input side of thepower-source controller 220 and the power regulation unit 240. The powersource 210 may be any type of rechargeable/replenishable source, or anytype of non-rechargeable/non-replenishable source operative to providepower to the IMD 110.

The power-source controller 220 preferably comprises circuitry forcontrolling and monitoring the flow of electrical power to variouselectronic and stimulation-delivery portions of the IMD 110 (such as thecomponents 230, 240, 250, 260 and 280 illustrated in FIG. 2). Moreparticularly, the power-source controller 220 is capable of monitoringthe power consumption or charge depletion of the IMD 110, measuring thevoltage across the power source 210, and generating elective replacementand/or end-of-service signals.

The communication unit 260 facilitates communication between the IMD 110and the control unit 150, as shown. The control unit 150 may be a devicethat is capable of programming various components and stimulationparameters of the IMD 110. In one embodiment, the control unit 150 is acomputer system capable of electronic communications, programming, andexecuting a data-acquisition program. The control unit 150 may becontrolled by a healthcare provider such as a physician in, for example,a doctor's office, or may be controlled by the patient. The control unit150 may be used to download various parameters and program software intothe IMD 110 for programming the operation of the IMD. The control unit150 may also receive and upload various status conditions and other datafrom the IMD 110. The communication unit 260 may comprise hardware,software executed by a processor, or any combination thereof.Communications between the control unit 150 and the communication unit260 may occur via a wireless or other type of communication, illustratedgenerally by line 275 in FIG. 2.

The power regulation unit 240 is capable of regulating power deliveredby the power source 210 to particular components of the IMD 110according to their needs and functions. The power regulation unit 240may perform a voltage conversion to provide appropriate voltages and/orcurrents for the operation of the components. The power regulation unit240 may comprise hardware, software executed by a processor, or anycombination thereof. The communication unit 260 is capable of providingtransmission and reception of electronic signals to and from a controlunit 150.

Stimulation controller 230 defines the electrical stimulation pulses tobe delivered as part of a burst to the nerve tissue according toparameters and waveforms that may be programmed into the IMD 110 usingthe control unit 150 or that may be pre-programmed into the controller230 prior to or after implantation of the IMD 110 into the patient'sbody. The stimulation controller 230 controls the operation of thestimulation unit 250, which generates the stimulation pulses comprisinga burst according to the parameters defined by the controller 230 and,in some embodiments, provides these pulses to the lead assembly 122 andelectrode assembly 125. Stimulation pulses provided by the IMD 110 mayvary widely across a range of parameters. The stimulation controller 230may comprise hardware, software executed by a processor, or anycombination thereof.

As previously explained, responsive, closed-loop bursts are delivered asa result of detecting some event. The detection logic 270 detectsvarious events that may trigger delivery of a stimulation burst by thestimulation logic 255 (stimulation controller 230 and stimulation unit250). For example, in some cases, the stimulation controller 230 and thestimulation unit 250 may deliver a stimulation burst in response todetection of an impending or already-occurring seizure based on one ormore of the patient's cardiac parameters (e.g., heart rate, rate ofchange of heart rate, heart rate variability, etc.). However, detectionlogic 270 may be implemented anywhere on the patient's body to detectany type of event. For example, the detection logic 270 may beconfigured to detect events such as patterns of electrical activity inthe brain, heart, or muscles, cardiac rhythms, blood pressure,respiratory patterns, etc. indicative of a condition treatable by theIMD. In some embodiments, the detection logic 270 may be disposed in alocation other than the patient's body to detect some other type ofevent independent of the patient's body (e.g., a request for astimulation burst initiated by the patient). Detection logic 270 mayinclude a sensor (e.g., a sensor that detects a condition of thepatient, or patient input, such as a tap or magnetic input apparatus).Further, the detection logic 270 may reside inside the IMD 110 and maybe comprised of hardware, software executable by a processor, or anycombination thereof. Upon detecting an event, the detection logic 270causes the stimulation controller 230 to activate the stimulation unit250 in response to the detected event. One or more of the blocks 210-280may comprise hardware, software executed by a processor, or anycombination thereof.

FIG. 3 shows a block diagram of the control unit 150, as shown in FIG.1, in accordance with various embodiments of the invention. The controlunit 150 includes a processor 302, storage 306, a display device 304, acommunication unit 314, and user input devices 316. The control unit 150may be implemented using any of various computing devices, such asdesktop computer, a laptop/notebook computer, a tablet computer, apersonal digital assistant (PDA), a smartphone, etc.

The processor 302 may a general purpose microprocessor, a digital signalprocessor, a microcontroller, or the like configured to executeinstructions retrieved from a computer readable medium. In general, aprocessor may include execution units (e.g., fixed point, floatingpoint, integer, etc.), storage (e.g., registers, memory, etc.),instruction decoding, peripherals (e.g., interrupt controllers, timers,direct memory access controllers, etc.), input/output systems (e.g.,serial ports, parallel ports, etc.) and various other components andsub-systems. Those skilled in the art understand that processors executesoftware instructions, and that software instructions alone areincapable of performing a function. Therefore, any reference to afunction performed by software, or to software performing a function issimply a shorthand means for stating that the function is performed by aprocessor executing the software, or a processor executing the softwareperforms the function.

The display device 304 may be a video display device, such as a liquidcrystal display, a cathode ray display, a plasma display, an organiclight emitting diode display, a vacuum fluorescent display, anelectroluminescent display, an electronic paper display, a projectiondisplay, or other type of display or output device suitable forconveying information to a user. The display device 304 may be coupledto the processor 304 via a graphics adapter (not shown), or by othertechniques known in the art. For example, the display device 304 may beremote from the processor 302 and data to be displayed may betransferred from the processor 302 to the display device 304 via anetwork.

The communication unit 314 may be configured to provide the control unit150 with one or modes of communication. The communication unit 314 mayprovide wireless communication with the IMD 110 via one or more channelsin the MICS. Communication with the programming wand 155 may be providedusing any of a variety of wired signaling protocols (e.g., RS-232,RS-485, universal serial bus, etc) or any other wireless signalingprotocols. The communication unit 314 may also allow the control unit150 to connect to one or more wired or wireless networks, for example, anetwork in accordance with IEEE 802.11, IEEE 802.3, Ethernet, a cellularnetwork, etc.

The user input device 316 allows a user (e.g., a physician) to controland/or provide information to the control unit 150. The user inputdevice 316 may, for example, be any one or more of a keyboard, a mouse,a trackball, a touchpad, a touch screen, a keypad, buttons, a microphoneand voice recognition system, a camera, a motion detection system, etc.The processor 302 may provide control information to the user inputdevice 316, and Information input via the user input device 316 istransferred to and manipulated by the processor 302.

The storage 306 is a computer readable medium that may storeinstructions for execution by the processor 302, and other data for useby the processor 302. The storage 302 may include one or more types ofnon-volatile and/or volatile memory including: a hard disk, an opticaldisk, FLASH memory, read-only memory, random access memory, and/or othertypes of magnetic, optical, or semiconductor storage. The storage 306may be external to the IMD 110 or may be the storage 280 of FIG. 2.Additionally, the execution of one or more of the instructions may beperformed by the processor 225 of FIG. 2. The data stored in the storage306 may be used by the processor 225 of FIG. 2.

The storage 306 stores life estimate/display generation data 312,stimulation/detection control data 310, and IMD life estimates data 308.The life estimate/display generation data 312 and thestimulation/detection control data 310 may include instructions that areexecutable by the processor 302. The life estimate/display generationdata 312 includes instructions, that when executed by the processor 302,estimate the operable life of the IMD 110 (i.e., estimates the life ofthe power source 210), and generates displays of the operable lifeestimates for viewing on the display device 304. The operable life orlongevity of the IMD 110 is the time period over which the power source210 provides sufficient energy to guarantee proper operation of the IMD110. The operable life estimates generated by the processor 302 usingthe life estimate/display generation data 312 are based on the capacityof the power source 210 consumed (e.g., charge consumed) by open-loopstimulation and closed-loop stimulation (automatic andmanually-initiated). Because the rate of future closed-loop stimulationsto be provided affects power source 210 life, but is difficult toaccurately ascertain, some embodiments of the life estimate/displaygeneration data 312 predict power source 210 life based on a measuredrate of past closed-loop stimulation or past closed-loop stimulationtrigger events recorded by the IMD 110 during an operating session (aninterval of, for example, a period of weeks).

Some embodiments of the life estimate/display generation module 312compute a power source life estimate (i.e., an estimate of the operablelife of the IMD 110) based on the number of open-loop stimulations,automatic stimulations/stimulation requests, and manually-initiatedstimulations/stimulation requests recorded by the IMD 110 in anoperating session, in conjunction with the corresponding stimulationparameters (e.g., stimulation pulse width, current, frequency, etc.)applicable to each stimulation category (e.g., open-loop, automatic,manual). Operable life estimates provided by such embodiments mayreflect the predicted life of the power source 210 based on theapplication of the measured rate of stimulation for each stimulationcategory using the corresponding stimulation parameters over the entirelife of the power source 210. That is, an operable life estimatepredicts what the life of the power source 210 would be if measuredstimulation rates and corresponding stimulation parameters were appliedover the full (i.e., from beginning to end) life of the IMD 110.

A life estimate display generated from the life estimate/displaygeneration data 312 identifies what portions of the total estimatedoperable life of the IMD 110 are consumed by open-loop stimulations,automatic stimulations, and manually-initiated stimulations. Byproviding the operable life estimate display based on stimulationcategories, the control unit 150 allows the user to adjust thestimulation/detection parameters to provide more or less detectionsensitivity for automatic stimulation events, and more or less energyper stimulation for each stimulation category thereby tuning operationof the IMD 110 to achieve a desired operable IMD life. For example, ifautomatic stimulations are judged, based on a display of operable IMDlife, to be consuming excessive IMD life, then the user may reduce thesensitivity of event detection that initiates automatic stimulation,thereby reducing the number of events detected, or the user may reducethe stimulation energy applied in response to a detected event.

The stimulation/detection control module 310, when executed by theprocessor 302, allows the user to input information for controlling thesensitivity of event detection for automatic stimulation. FIG. 4A showsan exemplary display 480 included in a graphical user interface withcontrol and input features provided by the stimulation/detection controlsoftware 310. A level of event detection sensitivity may entered by auser via a control feature, such as the sliders 482, 486, the text boxes484, 488, etc.

The stimulation/detection control software 310 allows the user tocontrol whether the IMD 110 provides stimulation in response to adetected event in addition to logging the detection of the event.Buttons 490 (e.g., radio buttons) provide the logging/stimulationselection. The capability to log detected events without providingautomatic stimulation can be useful for determining the number of eventsdetected at a particular sensitivity level without a correspondingreduction in IMD life.

The display 480 also includes a graphical display 492 of the estimatedlife of the IMD 110. The estimated life display 492 is broken down intosegments 494, 496, and 498 showing a portion of total IMD liferespectively consumed by open-loop, automatic, and manually-initiatedstimulations. The estimated life display segment 496 corresponding toautomatic stimulation is updated in response to changing the eventdetection sensitivity, thereby providing the user with feedbackregarding the effect of a change in sensitivity on IMD life. Anindication is made to the user (e.g., via the graphical display 492) todelineate actual counts (e.g., from previous recording intervals).

FIG. 4B shows an exemplary display 460, included in a graphical userinterface generated by the stimulation/detection control module 310, forsetting parameters (e.g., frequency, pulse width, etc.) related toopen-loop, automatic, and manually-initiated stimulations. Eachparameter is user adjustable using a control feature, such as the slider462, the text box 464, etc. Changes to these parameters may affect theoperable life of the IMD 110, and therefore may be reflected in anupdate of the graphical display of operable life provided to the user(e.g., display 492).

FIG. 4C shows an exemplary display 440, included in a graphical userinterface generated by the stimulation/detection control module 310, forsetting dose schedule and setting output current for open-loop,automatic, and manually-initiated stimulations. Each parameter is useradjustable using a control feature, such as the slider 442, the text box444, etc. The display 440 also includes a graphical display 446 of theestimated life of the IMD 110 based on stimulation and detectionparameters used by the IMD 110 during a previous use interval (e.g., thelast use session). An additional graphical display 448 of estimated IMDlife shows predicted IMD life based on the current setting applied tothe stimulation and detection parameters. Thus, changes in the currentand/or dose settings are reflected in the graphical display 448 forcomparison with the display 446 of estimated life based on thepreviously used parameters and IMD recorded stimulation information. Theestimated life displays 446, 448 are broken into segments showing aportion of total IMD life respectively consumed by open-loop, automatic,and manually-initiated stimulations.

A plurality of life estimates 308 may be recorded in the storage 282 and306. Each stored life estimate corresponds to a log of stimulations anddetected events recorded by the IMD 110 during an operating session, andthe stimulation parameters applied during the operating session. One ormore of the recorded life estimates may be displayed to provide ahistory of life estimates for the IMD 110. FIG. 4D shows a graphicaldisplay 400 of a plurality of life estimates 308. Each life estimatecorresponds to a stored life estimate as described above, and shows aportion of IMD 110 operable life consumed by open-loop, automatic, andmanually-initiated stimulations. For example, based on the use of theIMD 110 during the operating session of Interval A, which may be aperiod of weeks, the operable life of the IMD 110 is estimated to beless than 5 years. Any number of parameters, in addition to thoseprovided in FIGS. 4A-D, may be provided to modify the different types ofstimulation. For example, a physician may set a threshold that limitsthe number of manually-initiated stimulations within a period of time tolimit battery consumption and health risks (e.g., side effects) fromunnecessary stimulation.

FIG. 5 shows a flow diagram of an illustrative method for predictinglongevity of the IMD 110 in accordance with various embodiments of theinvention. Though depicted sequentially as a matter of convenience, atleast some of the actions shown can be performed in a different orderand/or performed in parallel. Additionally, some embodiments may performonly some of the actions shown. Embodiments of the method may beimplemented by the IMD 110 and/or the control unit 150 as disclosedherein. In some embodiments, at least some of the operations of FIG. 5,as well as other operations described herein, can be implemented asinstructions stored in a computer readable medium and executed by aprocessor.

In block 502, a user of the control unit 150 assigns a first set ofvalues to IMD control parameters. The control parameters may includeopen-loop stimulation rate and level, automatic stimulation level,manually-initiated stimulation level, event detection level forautomatic stimulation, and automatic and manually-initiatedstimulation/logging enablement controls. The first set of valuesconfigures the IMD 110 to provide open-loop stimulation. The rate andlevel of open-loop stimulation may be selected to provide the IMD 110with a desired longevity (e.g., 5-6 years). The first set of values mayfurther configure the IMD 110 to disable automatic stimulation andmanually-initiated stimulation, while enabling logging of detection ofevents that trigger automatic stimulation and logging of requests formanually-initiated stimulation. If disabled, automatic andmanually-initiated stimulation do not contribute to depletion of thepower source 210, but detected event logging allows for acquisition ofpotential stimulation information that can be used to estimate energyconsumption had closed-loop stimulation been enabled.

In some embodiments, archived longevity data (e.g., generalizedlongevity information based on measured longevity of previouslyimplanted IMDs using known open-loop and/or closed-loop stimulationparameters) may be applied to select the open-loop and closed-loopstimulation parameters and to estimate longevity of the IMD 110. Thearchived longevity data may be non-patient specific, and may beparticularly useful in estimating IMD longevity before patient specificlongevity information is acquired. However, embodiments may applyarchived longevity data to estimating the longevity of the IMD 110,alone or in combination with patient specific longevity information, atany point in the life of the IMD 110.

In block 504, the IMD 110 is operated for a first interval (e.g., asession covering a period of weeks) as configured by the first set ofvalues. The IMD 110 provides open-loop stimulation, and records thenumber of open-loop stimulations, the number of detected automaticstimulation events, and the number of requests for manually-initiatedstimulation in a log 282 in the storage 280.

In block 506, at the completion of the operating session, the controlunit 150 retrieves the stimulation and detected event information loggedby the IMD 110 during the operating session. The control unit 150 mayretrieve the logged information via the communication units 260, 314.Alternatively, the IMD 110 provides the information to the control unit150 during the operating session.

In block 508, the control unit 150 estimates the operable life of theIMD 110 based on the retrieved stimulation and detected eventinformation. The IMD life estimate is further based on the stimulationlevel parameters (e.g., stimulation current, pulse width, etc.) used bythe IMD 110 during the operating session. The stimulation levelparameters may be transferred from the IMD 110 to the control unit 150,or retrieved from control unit storage 306. In some embodiments, IMDlife estimation includes determining the energy consumed by thestimulations administered, and stimulations that would have beenadministered had automatic or manually-initiated stimulation beenenabled, and determining the life of power source 210 if the determinedsession energy consumption were applied over the entire life of thepower source 210. The portion of total power source energy consumed byeach category of stimulation may be determined based on the number ofstimulations and the charge consumption or potential charge consumptionper stimulation for the category during the operating session.

In block 510, the control unit 150 presents a display (e.g., display400) of the estimated longevity of the IMD 110. The display shows thetotal estimated life of the IMD 110, and shows what portion of the totalestimated life is consumed by each of open-loop stimulation, automaticstimulation, and manually-initiated stimulation based on the stimulationrate, stimulation level, and other stimulation parameters applied duringthe operating session. IMD life display 402 of FIG. 4D is an example ofa display of an IMD life estimate wherein the IMD 110 is operated usingopen-loop stimulation configured to provide an estimated six year powersource life, automatic and manually-initiated stimulation are disabled,and detected automatic stimulation events and requests formanually-initiated stimulation are logged.

In block 512, the IMD control values are adjusted based on the estimatedIMD life. Open-loop stimulation rate and/or level may be adjusted toallow for the anticipated energy consumption of automatic andmanually-initiated stimulation. Automatic stimulation event detectionsensitivity may be adjusted based on the number and/or level of eventsdetected in the previous operating session. Stimulation levels forautomatic and/or manually-initiated stimulation may be adjusted toprovide a desired longevity for the power source 210. Automatic and/ormanually-initiated stimulation may be disabled to allow for furtheracquisition of detected event information without affecting the life ofthe power source 210, or automatic and/or manually-initiated stimulationmay be enabled.

In block 514, the control unit 150 generates a new operable lifeestimate for the IMD 110 based on the adjusted IMD control values. Adisplay representing the new estimate of IMD life is presented, by thecontrol unit 150, in block 516. The display shows total estimated IMDlife and portions of IMD life allocated to open-loop, automatic, andmanually-initiated stimulation allowing the user to further adjust thestimulation parameters and receive immediate feedback as to the effectsof the adjustments on IMD life.

IMD life display 404 of FIG. 4D is an example of a display of an IMDlife estimate wherein the automatic stimulation level and/or detectionsensitivity has been adjusted based on the detected number of automaticstimulation events (or IMD life potentially consumed by automaticstimulation events) of the prior operating session (as shown in display402). The IMD 110 is operated for a second session (FIG. 4D, Interval B)using open-loop stimulation configured to provide an estimated six yearpower source life, automatic stimulation and manually-initiatedstimulation are disabled, and detected closed-loop stimulation eventsare logged.

IMD life display 406 of FIG. 4D is an example of a display of an IMDlife estimate wherein the open-loop stimulation rate and level has beenadjusted to reduce the scheduled open-loop stimulation, but theautomatic stimulation and manually-initiated stimulation remainunchanged. The IMD 110 is operated for a third session (Interval C) withopen-loop stimulation, automatic stimulation, and manually-initiatedstimulation enabled and configured to provide an estimated 6 yearoperational life for the IMD 110. Thus, the desired six year operationallife is maintained over the various operating sessions while adjustingoperating parameters applied to the different categories of stimulation.

The efficacy of the therapy may be considered when adjusting the therapyparameters to provide the most efficacious therapy using the leastamount of power. The adjustments to the parameters and considerations ofefficacy and battery life may be applied in an iterative fashion. Inthis manner, the needed level of therapy may be provided to the patientwhile maximizing the life of the IMD power source.

The above discussion is meant to be illustrative of various principlesand embodiments of the present invention. Numerous variations andmodifications will become apparent to those skilled in the art once theabove disclosure is fully appreciated. For example, while embodimentshave been described with reference to estimating power source longevity,those skilled in the art will understand that embodiments are alsoapplicable to estimating the longevity of other depletable resources(e.g., a drug supply) of an IMD. It is intended that the followingclaims be interpreted to embrace all such variations and modifications.

What is claimed is:
 1. A system for estimating a life of a power sourceof an implantable medical device (IMD), the system comprising: a therapylogic, wherein the therapy logic provides: an open-loop stimulationtherapy; and a closed-loop stimulation therapy, wherein the closed-loopstimulation therapy comprises at least one of: a patient initiatedstimulation therapy; and an event detection stimulation therapy; adetection logic, wherein the detection logic: detects a change in one ormore body parameters; detects a patient input; and triggers a changefrom the open-loop stimulation to the closed loop stimulation therapybased upon a detection of either a change in one or more body parameteror a patient input; and a control device, wherein the control device:calculates an open-loop life estimate of the power source, wherein theopen-loop life estimate is based upon a set of open-loop stimulationparameters; calculates a closed-loop charge consumption, wherein theclosed-loop charge consumption is based upon a set of closed loopstimulation parameters; and provides a first operable life estimate,wherein the first operable life estimate comprises a differenceresulting from subtracting the closed-loop charge consumption from theopen-loop life estimate.
 2. The system of claim 1, wherein the controldevice is configured to update the first operable life estimate based onchanging a parameter value corresponding to the open-loop therapy. 3.The system of claim 1 further comprising a communication logic, whereinthe communication logic is configured to retrieve control informationfrom the IMD and to provide the estimate of operable life to an externaldevice.
 4. The system of claim 1, wherein at least one of the open-loopstimulation parameters comprises at least one of: a time period; a dutycycle, wherein the duty cycle comprises a ratio of an on-time to acombination of the on-time and an off-time; a current magnitude; a pulsewidth; a frequency; and burst duration.
 5. The system of claim 1,wherein at least one of the closed-loop stimulation parameters comprisesat least one of: a time period; a duty cycle, wherein the duty cyclecomprises a ratio of an on-time to a combination of the on-time and anoff-time; a current magnitude; a pulse width; a frequency; and burstduration.
 6. The system of claim 1, wherein the detection logicspecifies a detection level associated with each of the one or more bodyparameters.
 7. The system of claim 1, wherein the estimate of operablelife represents the entire life of the power source.
 8. The system ofclaim 1, wherein the control device is further configured to store aplurality of operable life estimates.
 9. The system of claim 1, whereinthe control device is configured to update the first operable lifeestimate based on changing a parameter value corresponding to theclosed-loop therapy.
 10. A method for estimating a life of a powersource of an implantable medical device (IMD), the method comprising:providing: an open-loop stimulation therapy; and a closed-loopstimulation therapy, wherein the closed-loop stimulation therapycomprises at least one of: a patient initiated stimulation therapy; andan event detection stimulation therapy; detecting: a change in one ormore body parameters; and a patient input; triggering a change from theopen-loop stimulation to the closed loop stimulation therapy based upona detection of either a change in one or more body parameter or apatient input; and calculating an open-loop life estimate of the powersource, wherein the open-loop life estimate is based upon a set ofopen-loop stimulation parameters; calculating a closed-loop chargeconsumption, wherein the closed-loop charge consumption is based upon aset of closed loop stimulation parameters; and providing a firstoperable life estimate, wherein the first operable life estimatecomprises a difference resulting from subtracting the closed-loop chargeconsumption from the open-loop life estimate.
 11. The method of claim 10further comprising updating the first operable life estimate based onchanging a parameter value corresponding to the open-loop therapy. 12.The method of claim 10 further comprising updating the first operablelife estimate based on changing a parameter value corresponding to theclosed-loop therapy.
 13. The method of claim 10 further comprising aproviding the first operable life estimate to an external device. 14.The method of claim 10, wherein at least one of the open-loopstimulation parameters comprises at least one of: a time period; a dutycycle, wherein the duty cycle comprises a ratio of an on-time to acombination of the on-time and an off-time; a current magnitude; a pulsewidth; a frequency; and burst duration.
 15. The method of claim 10,wherein at least one of the closed-loop stimulation parameters comprisesat least one of: a time period; a duty cycle, wherein the duty cyclecomprises a ratio of an on-time to a combination of the on-time and anoff-time; a current magnitude; a pulse width; a frequency; and burstduration.
 16. The method of claim 10 further comprises specifying adetection level associated with each of the one or more body parameters.17. The method of claim 10, wherein the first operable life estimaterepresents the entire life of the power source.
 18. The method of claim10 further comprising store a plurality of operable life estimates.